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Pilot Operated Check Valve

The cylinder in this schematic will tend to creep due to valve leakage

According to the schematic above the cylinder should remain in its position when the control valve is in its center position or off position. But in practice the leakage in control valve will allow the cylinder to creep.

Check valve would not have any leakage in closed position but we can’t use a simple check valve to the schematic above because the flow is required in both directions. We can use pilot operated check valve to solve the problem, the valve is similar to basic check valve with port for external pilot pressure signal to open the valve in both direction.

In the 4C pilot operated check valve the pilot pressure will open the poppet to allow free flow in both directions. We can re-draw the existing schematic to the schematic below where we add a pilot operated check valve. The valve’s pilot lines are connected to the pressure line source of the other side of cylinder. If the cylinder moves, one check valve is operated as normal check valve and the other check valve operated by pilot pressure. If we need the cylinder to stop in its position, the cylinder will held in its position because the both check valve are closed and not allowing any flow.